The present invention relates to a polishing composition to be used in polishing, for example, for forming the wiring of a semiconductor device.
When the wiring of a semiconductor device is formed, firstly, a barrier layer and a conductor layer are sequentially formed in this order on an insulator layer having trenches therein. After that, at least portions of the conductor layer (outside portions of the conductor layer), which is positioned outside the trenches, and portions of the barrier layer (outside portions of the barrier layer), which is positioned outside the trenches, are removed by chemical mechanical polishing. A polishing process for removing at least the outside portions of the conductor layer and the outside portions of the barrier layer is usually conducted by divided steps of the first polishing step and the second polishing step. In the first polishing step, a part of the outside portions of the conductor layer is removed so as to expose the upper surface of the barrier layer to the outside. In the subsequent second polishing step, at least the remaining outside portions of the conductor layer and the outside portion of the barrier layer are removed so as to expose the insulator layer to the outside and obtain a flat surface.
It has been proposed to use a polishing composition containing a surfactant so as to improve the flatness of an object to be polished after having been polished as a polishing composition to be used in such polishing for forming the wiring of a semiconductor device and particularly in polishing of the second polishing step. Japanese Laid-Open Patent Publication No. 2008-41781 discloses a polishing composition containing an anionic surfactant such as ammonium polyoxyethylene lauryl ether sulfate, an anticorrosive such as benzotriazole, and a nonionic surfactant such as a polyoxyethylene alkyl ether. International Publication No. WO 2007/026862 discloses use of a surfactant such as a polyoxyethylene alkyl ether acetate and a polyoxyethylene alkyl ether phosphate in combination with at least one compound selected from benzotriazole and benzotriazole derivatives. Japanese Laid-Open Patent Publication No. 2005-109256 also discloses a polishing composition containing various surfactants.
However, the above described conventional polishing compositions aim at improving particularly the flatness of an object to be polished after having been polished, and have been insufficient in the point of reducing surface defects of the object to be polished that are formed due to polishing.